story problem

Question

a swimming pool holds
480,000
liters of water. The pool has two drainage pipes. When the pool is completely full, the first pipe alone can empty it in
240
minutes, and the second pipe alone can empty it in
160
minutes. When both pipes are draining together, how long does it take them to empty the pool?

Answer 1

Hi leo,

 

How much does pipe 1 empty in one minute

 

1/240

 

how much does pipe 2 empty in one minute

 

1/160

 

let x = time to empty working together

 

x/240 + x/160 = 1   (1 represents the full job

 

 

multipy by 480 to clear the fractions

 

2x + 3x = 480

 

5x = 480

 

x = 96    (minutes reuquired to empty pool with both pipes together

 

 

Hope this helps